The present invention relates to a novel positive-working photoresist composition or, more particularly, to a positive-working photoresist composition having excellent photosensitivity, resolving power and depth of focusing and capable of giving a patterned resist layer having excellent heat resistance and satisfactorily orthogonal cross sectional profile of the patterned resist layer with a remarkably suppressed standing wave effect or, namely, an adverse effect caused by the interference of the incident light to the resist layer and the reflecting light from the substrate surface.
As is well known, it is a remarkable trend in recent years in the manufacture of electronic devices such as ICs, LSIs, VLSIs and the like that the degree of integration is rapidly increasing year by year and the patterning works on the substrate such as semiconductor silicon wafers and the like are required to have extremely high fineness of submicron order, for example, in the manufacture of VLSIs. In order to comply with such a requirement, the photoresist composition or, in particular, the positive-working photoresist composition used for the photolithographic patterning work is also required to exhibit high performance relative to the photosensitivity, resolving power and depth of focusing as well as heat resistance of the patterned photoresist layer. In the modern photolithographic patterning process for the manufacture of VLSIs, furthermore, it is eagerly desired to develop a positive-working photoresist composition in which the adverse influence by the so-called standing wave effect is suppressed as completely as possible in addition to the above mentioned requirements. Nevertheless, it is the present status in the technology of photoresist compositions that a positive-working photoresist composition satisfying all of the above mentioned requirements is not available.
For example, Japanese Patent Kokai 2-971 proposes a method for the formation of a patterned resist layer by using a positive-working photoresist composition formulated with a hydroxybenzophenone of an increased degree of esterification as the photosensitive ingredient with an object to suppress the effects of intramembrane multipath reflection, the bulk effect and the standing wave effect. Although these undesirable phenomena can be suppressed to some extent in this positive-working photoresist composition, the improvement achieved in this composition is not quite satisfactory and, in addition, the performance thereof is not so high relative to the photosensitivity and the resolving power as to comply with the requirements in the manufacture of modern electronic devices such as VLSIs.